Methods of telecommunication between one main station and one terminal are conventional.
In the so-called Internet e-mail Service, messages are created by a so-called mail client and are transmitted via the Internet to a mail server of a recipient using the so-called SMTP (simple mail transfer protocol) according to RFC 821 (request for command) of the IETF (Internet Engineering Task Force), or using the ESMTP (enhanced simple mail transfer protocol) according to RFC 1869 of the IETF. The recipient can access the transmitted message from the mail server, also with the aid of a mail client. Appropriate protocols are used for access to the transmitted message, for instance, POP (post office protocol) according to RFC 1729 of IETF, or IMAP (Internet message access protocol) according to RFC 2060 of IETF, or even protocols specific to manufacturers. These protocols regulate the exchange of messages between the recipient and the mail server, such as, for instance, the logging on of a mail client to the mail server, authentication of the mail client, etc. For transmission of messages from mail server to mail client, SMTP or ESMTP are generally used. In order to register new messages on the mail server, the mail client checks the mail server sporadically or regularly. This procedure is called polling. If the mail client detects messages present on the mail server for the user of the mail client, it signals this to the user. The user can then initiate access to the message stored for him on the mail server. The initiation of access is also called pull mode. The message is then transmitted from mail server to mail client and can be reproduced there for the user. The method described here is intended essentially for dedicated connections, where the mail client has a permanent connection to the e-mail server, or a connection with relatively brief interruptions. SMTP was originally provided for text messages, by the use of MIME (multipurpose Internet mail extensions) according to RFC 1521 of IETF, such messages can be expanded by attachments. In this connection, the attachments can have any format desired, and are not limited to text messages. However, for transmission, these messages are recoded so that they can also be transmitted in the form of simple text messages.
The SMS service (short message service) according to the GSM standard (global system for mobile communications), GSM 03.40 ETSI differs fundamentally from the internet e-mail service described. It is limited exclusively to text messages having a maximum length of 160 characters, there being (the possibility of) expansions by concatenation of a plurality of such text messages. The SMS service is further based on transmitting the text message from an SMS transmitter to an SMS server, which then automatically transmits it to a mobile terminal. This method is also denoted as push mode. If the mobile terminal in the mobile radio network is not available, for instance, because it is switched off, the message is stored temporarily in the SMS server. Following that, when the mobile terminal can be reached again, this is signaled to the SMS server, and it automatically begins transmission of the text message to the mobile terminal.